It is difficult to economically produce hydrocarbons from low permeability reservoir rocks. Oil and gas production rates are often boosted by hydraulic fracturing, a technique that increases rock permeability by opening channels through which hydrocarbons can flow to recovery wells. During hydraulic fracturing, a fluid is pumped into the earth under high pressure (sometimes as high as 50,000 PSI) where it enters a reservoir rock and cracks or fractures it. Large quantities of proppants are carried in suspension by the fluid into the fractures. When the pressure is released, the fractures partially close on the proppants, leaving channels for oil and gas to flow.
Specialized pumps are used to deliver fracture fluids at sufficiently high rates and pressures to complete a hydraulic fracturing procedure or “frac job.” These pumps are usually provided with fluid ends having both reciprocating plungers that place fluids under pressure and valves that control fluid flow to and from the plungers. Fluid ends have many parts that are releasably fastened to one another so that they can be easily repaired or replaced. It is the connections between the parts and the supporting features for the valves that tend to weaken a fluid end, limiting its pressure rating, and making it susceptible to corrosion, leaks, and cracks under high, cyclical stresses. Thus, fluid ends sometimes fail under load prematurely.
In an effort to increase pressure ratings and decrease failure rates, “Y-type” fluid ends have been proposed by oilfield pump manufacturers. Y-type fluid ends reduce concentrated stresses in the body of a fluid end by increasing the angles at which the principal flow channels within the body intersect one another to about 120°, reducing cyclical loading. Few of the proposed Y-type designs have seen widespread use or commercial success since they have been difficult and costly to make and equally difficult to service in the field. A continuing need, therefore, exists for a strong and reasonably priced, Y-type fluid end that delivers fracture fluids to reservoir rocks at very high rates and pressures.